Reference

The transportation of oil through the Kazakhstan–China oil pipeline involves several key companies:

1. KazTransOil: This company is the national oil pipeline operator in Kazakhstan and is involved in transporting oil through its diversified network of pipelines. KazTransOil is part of the National Company KazMunayGas.
2. China National Petroleum Corporation (CNPC): This company operates through its subsidiary, China National Oil and Gas Exploration and Development Corporation (CNODC). CNPC has a joint venture with KazMunayGas for the Kazakhstan-China Pipeline.

In summary, the primary companies responsible for transporting oil through the Kazakhstan–China oil pipeline are KazTransOil and China National Petroleum Corporation (CNPC), along with their respective subsidiaries.

For more detailed information, you can refer to the sources:

• Kazakhstan–China Oil Pipeline - Global Energy Monitor
• Kazakhstan–China oil pipeline - Wikipedia

Here are a couple of images of the pipeline routes: